Changes:
* LeafNode is aligned to LEAF_PAGE_SIZE.
Alignment brings 24 bytes memory overhead for 4096, but reduces
cache misses rate.
* Unused m_element_count from leaf nodes file.
The size is computed as m_leaves_region.size() / LEAF_PAGE_SIZE.
* Added try/catch for mmap exceptions messages.
StaticRTree now uses projected coordinates internally. That means we can
use a euclidean distance measure (squared distance) for sorting the
query queue.
Small fixes I didn't want to include in unrelated PRs.
There are a few left in `storage.cpp` but since it's a single function
in 600 lines of code, I didn't want to touch the mess. The others are
safe to remove, cucumber and test run on Finland gives 👍.
rather than being cached in the StaticRTree. This means we
can freely apply traffic data and not have stale values lying
around. It reduces the size of the RTree on disk, at the expense
of some additional data in RAM.
